Discovery by operating system of information relating to adapter functions accessible to the operating system

ABSTRACT

A tiered discovery capability is employed to obtain attributes regarding adapters of an I/O configuration. The first tier obtains a list of the adapter functions accessible to an operating system; the second tier obtains attributes regarding a selected adapter function of the list of adapter functions; and a third tier obtains common attributes of a group of adapter functions, the group including the selected adapter function.

BACKGROUND

This invention relates, in general, to input/output (I/O) processing ina computing environment, and in particular, to obtaining informationregarding the I/O configuration of the computing environment.

Different computing architectures have different I/O configurations. Forinstance, System z® machines based on the z/Architecture® offered byInternational Business Machines Corporation have an I/O configurationthat includes a channel subsystem having channels and subchannels.Associated with this channel subsystem is an interface, referred to as aChannel Subsystem Call instruction, by which operating systems canmanipulate the various I/O resources of the configuration.

Other types of I/O configurations, however, may be used that do notinclude traditional I/O devices, such as channels and subchannels. Forinstance, some configurations use Peripheral Component Interconnect(PCI) adapters, which have attachment and communication paradigms thatare different than that of traditional I/O devices.

BRIEF SUMMARY

In accordance with an aspect of the present invention, a capability isprovided for obtaining information regarding an I/O configuration thatincludes adapters, such as PCI adapters.

The shortcomings of the prior art are overcome and advantages areprovided through the provision of a computer program product forobtaining I/O hardware information. The computer program productincludes a computer readable storage medium readable by a processingcircuit and storing instructions for execution by the processing circuitfor performing a method. The method includes, for instance, responsiveto execution of an instruction issued by an operating system obtaining,by a processor of a computing environment, a list of one or more adapterfunctions of an I/O configuration accessible by the processor, theoperating system absent knowledge of an adapter configuration topologyof adapter functions of the computing environment, and the listincluding one or more function handles corresponding to the one or moreadapter functions; and responsive to execution of an instruction issuedby the operating system, using a function handle of the one or morefunction handles to obtain one or more attributes regarding the adapterfunction identified by the function handle, the function handle usableby one or more instructions to access the adapter function correspondingto the function handle.

Methods and systems relating to one or more aspects of the presentinvention are also described and claimed herein. Further, servicesrelating to one or more aspects of the present invention are alsodescribed and may be claimed herein.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1A depicts one embodiment of a computing environment to incorporateand use one or more aspects of the present invention;

FIG. 1B depicts another embodiment of a computing environment toincorporate and use one or more aspects of the present invention;

FIG. 2 depicts one embodiment of further details of system memory andthe I/O hub of FIGS. 1A and 1B, in accordance with an aspect of thepresent invention;

FIG. 3A depicts one example of a function table entry used in accordancewith an aspect of the present invention;

FIG. 3B depicts one embodiment of a function handle used in accordancewith an aspect of the present invention;

FIG. 4 depicts one embodiment of the logic to discover informationrelating to adapter functions, in accordance with an aspect of thepresent invention;

FIG. 5A depicts one embodiment of a Call Logical Processor instructionused in accordance with an aspect of the present invention;

FIG. 5B depicts one embodiment of a request block used by the CallLogical Processor instruction of FIG. 5A for a list operation, inaccordance with an aspect of the present invention;

FIG. 5C depicts one embodiment of a response block for the listoperation of FIG. 5B, in accordance with an aspect of the presentinvention;

FIG. 5D depicts one embodiment of a function list entry used inaccordance with an aspect of the present invention;

FIG. 6A depicts one embodiment of a request block used by the CallLogical Processor instruction of FIG. 5A for a query function operation,in accordance with an aspect of the present invention;

FIG. 6B depicts one embodiment of a response block for the queryfunction operation of FIG. 6A, in accordance with an aspect of thepresent invention;

FIG. 7A depicts one embodiment of a request block used by the CallLogical Processor instruction of FIG. 5A for a query group operation, inaccordance with an aspect of the present invention;

FIG. 7B depicts one embodiment of a response block for the query groupoperation of FIG. 7A, in accordance with an aspect of the presentinvention;

FIG. 8 depicts one embodiment of a computer program productincorporating one or more aspects of the present invention;

FIG. 9 depicts one embodiment of a host computer system to incorporateand use one or more aspects of the present invention;

FIG. 10 depicts a further example of a computer system to incorporateand use one or more aspects of the present invention;

FIG. 11 depicts another example of a computer system comprising acomputer network to incorporate and use one or more aspects of thepresent invention;

FIG. 12 depicts one embodiment of various elements of a computer systemto incorporate and use one or more aspects of the present invention;

FIG. 13A depicts one embodiment of the execution unit of the computersystem of FIG. 12 to incorporate and use one or more aspects of thepresent invention;

FIG. 13B depicts one embodiment of the branch unit of the computersystem of FIG. 12 to incorporate and use one or more aspects of thepresent invention;

FIG. 13C depicts one embodiment of the load/store unit of the computersystem of FIG. 12 to incorporate and use one or more aspects of thepresent invention; and

FIG. 14 depicts one embodiment of an emulated host computer system toincorporate and use one or more aspects of the present invention.

DETAILED DESCRIPTION

In accordance with an aspect of the present invention, a capability isprovided for obtaining by an operating system (or other software, suchas other programs, etc.) input/output (I/O) hardware informationrelating to adapters of an I/O configuration. (As used herein, the termoperating system includes operating system device drivers). Thisinformation may be obtained absent knowledge of a definition of the I/Oconfiguration. That is, no knowledge of the types of adapters in theconfiguration nor any knowledge of the configuration topology is neededby the operating system. The operating system does not need to perform abus walk to obtain the adapter information; indeed, in a partitioned orotherwise virtualized computing environment, for example, the operatingsystem is not permitted to perform the bus walk. Instead, the firmwareperforms the bus walk, and the operating system is able to obtain theinformation without a bus walk.

As used herein, firmware includes, e.g., the microcode, millicode and/ormacrocode of the processor. It includes, for instance, thehardware-level instructions and/or data structures used inimplementation of higher level machine code. In one embodiment, itincludes, for instance, proprietary code that is typically delivered asmicrocode that includes trusted software or microcode specific to theunderlying hardware and controls operating system access to the systemhardware.

Further, the term adapter includes any type of adapter (e.g., storageadapter, processing adapter, network adapter, crypto adapter, PCIadapter, other type of input/output adapters, etc.). Moreover, in theexamples presented herein, adapter is used interchangeably with adapterfunction (e.g., PCI function), unless otherwise noted. In oneembodiment, an adapter includes one adapter function. However, in otherembodiments, an adapter may include a plurality of adapter functions.One or more aspects of the present invention are applicable whether anadapter includes one adapter function or a plurality of adapterfunctions. In one embodiment, if an adapter includes a plurality ofadapter functions, then each adapter function may be discovered inaccordance with an aspect of the present invention.

One embodiment of a computing environment to incorporate and use one ormore aspects of the present invention is described with reference toFIG. 1A. In one example, a computing environment 100 is a System z®server offered by International Business Machines Corporation. System z®is based on the z/Architecture® offered by International BusinessMachines Corporation. Details regarding the z/Architecture® aredescribed in an IBM® publication entitled, “z/Architecture Principles ofOperation,” IBM Publication No. SA22-7832-07, February 2009, which ishereby incorporated herein by reference in its entirety. IBM®, System z®and z/Architecture® are registered trademarks of International BusinessMachines Corporation, Armonk, N.Y. Other names used herein may beregistered trademarks, trademarks or product names of InternationalBusiness Machines Corporation or other companies.

In one example, computing environment 100 includes one or more centralprocessing units (CPUs) 102 coupled to a system memory 104 (a.k.a., mainmemory) via a memory controller 106. To access system memory 104, acentral processing unit 102 issues a read or write request that includesan address used to access system memory. The address included in therequest is typically not directly usable to access system memory, andtherefore, it is translated to an address that is directly usable inaccessing system memory. The address is translated via a translationmechanism (XLATE) 108. For example, the address is translated from avirtual address to a real or absolute address using, for instance,dynamic address translation (DAT).

The request, including the address (translated, if necessary), isreceived by memory controller 106. In one example, memory controller 106is comprised of hardware and is used to arbitrate for access to thesystem memory and to maintain the memory's consistency. This arbitrationis performed for requests received from CPUs 102, as well as forrequests received from one or more adapters 110. Like the centralprocessing units, the adapters issue requests to system memory 104 togain access to the system memory.

In one example, adapter 110 is a Peripheral Component Interconnect (PCI)or PCI Express (PCIe) adapter that includes one or more PCI functions. APCI function issues a request that is routed to an input/output hub 112(e.g., a PCI hub) via one or more switches (e.g., PCIe switches) 114. Inone example, the input/output hub is comprised of hardware, includingone or more state machines.

The input/output hub includes, for instance, a root complex 116 thatreceives the request from a switch. The request includes an input/outputaddress that is used to perform a direct memory access (DMA) operationor to request a message signaled interruption (MSI), as examples. Thisaddress is provided to an address translation and protection unit 118which accesses information used for either the DMA or the MSI request.

In a further embodiment of a computing environment, in addition to orinstead of one or more CPUs 102, a central processing complex is coupledto memory controller 106 as shown in FIG. 1B. In this example, a centralprocessing complex 150 includes, for instance, one or more partitions orzones 152 (e.g., logical partitions LP1-LPn), one or more centralprocessors (e.g., CP1-CPm) 154, and a hypervisor 156 (e.g., a logicalpartition manager), each of which is described below.

Each logical partition 152 is capable of functioning as a separatesystem. That is, each logical partition can be independently reset,initially loaded with an operating system or a hypervisor (such as z/VM®offered by International Business Machines Corporation, Armonk, N.Y.),if desired, and operate with different programs. An operating system, ahypervisor, or an application program running in a logical partitionappears to have access to a full and complete system, but only a portionof it is available. A combination of hardware and Licensed Internal Code(also referred to as microcode or millicode) keeps a program in alogical partition from interfering with the program in a differentlogical partition. This allows several different logical partitions tooperate on a single or multiple physical processors in a time slicemanner. In this particular example, each logical partition has aresident operating system 158, which may differ for one or more logicalpartitions. In one embodiment, operating system 158 is a z/OS® or zLinuxoperating system, offered by International Business MachinesCorporation, Armonk, N.Y. z/OS® and z/VM® are registered trademarks ofInternational Business Machines Corporation, Armonk, N.Y.

Central processors 154 are physical processor resources that areallocated to the logical partitions. For instance, a logical partition152 includes one or more logical processors, each of which representsall or a share of the physical processor resource 154 allocated to thepartition. The underlying processor resource may either be dedicated tothat partition or shared with another partition.

Logical partitions 152 are managed by hypervisor 156 implemented byfirmware running on processors 154. Logical partitions 152 andhypervisor 156 each comprise one or more programs residing in respectiveportions of central storage associated with the central processors. Oneexample of hypervisor 156 is the processor Resource/Systems Manager(PR/SM), offered by International Business Machines Corporation, Armonk,N.Y.

Although, in this example, a central processing complex having logicalpartitions is described, one or more aspects of the present inventionmay be incorporated in and used by other processing units, includingsingle or multi-processor processing units that are not partitioned,among others. The central processing complex described herein is onlyone example.

Further details regarding system memory and the input/output hub aredescribed with reference to FIG. 2. In this example, the memorycontroller is not shown, but may be used. The I/O hub may be coupled tosystem memory 104 and/or processor 204 directly or via a memorycontroller.

Referring to FIG. 2, in one example, system memory 104 includes one ormore address spaces 200. An address space is a particular portion ofsystem memory that has been assigned to a particular component of thecomputing environment, such as a particular adapter. In one example, theaddress space is accessible by direct memory access (DMA) initiated bythe adapter, and therefore, an address space is referred to in theexamples herein as a DMA address space. However, in other examples,direct memory access is not used to access the address space.

A DMA address space is assigned to a particular adapter by, forinstance, an operating system (e.g., operating system 202) executingwithin a processor 204 (e.g., CPU 102 or a CP 154 assigned to an LP152). This assignment is performed via a registration process, whichcauses an initialization (via, e.g., trusted software) of a device tableentry 210 for that adapter. There is one device table entry per assignedaddress space. The device table entry is located in a device table 212located in I/O hub 112. For example, device table 212 is located withinthe address translation and protection unit of the I/O hub.

In one example, device table entry 210 includes information 214 usablein providing various services for the adapter. For example, the devicetable entry may include an enable indicator that indicates whether thedevice table entry is enabled for a particular adapter; information tofacilitate address translation and/or interrupt handling; and/or otherinformation depending on the service to be performed.

In one embodiment, the device table entry to be used by a particularadapter issuing requests is located using a requestor identifier (RID)(and/or a portion of the address) located in a request issued by a PCIfunction 220 associated with an adapter. The requestor id (e.g., a16-bit value specifying, for instance, a bus number, device number andfunction number) is included in the request as well as an I/O address tobe used. The request, including the RID and the I/O address, areprovided to, e.g., a contents addressable memory (CAM) 230 via, e.g.,one or more switches 114, which is used to provide an index value. Forinstance, the CAM includes multiple entries, with each entrycorresponding to an index into the device table. Each CAM entry includesthe value of a RID. If, for instance, the received RID matches the valuecontained in an entry in the CAM, a corresponding device table index isused to locate the device table entry. That is, the output of the CAM isused to index into device table 212 to locate device table entry 210. Ifthere is no match, the received packet is discarded. (In otherembodiments, a CAM or other lookup is not needed and the RID is used asthe index.)

In addition to a device table entry, another data structure is alsoassociated with an adapter, which includes information regarding theadapter. In one or more particular examples described herein, the termadapter refers to an adapter function (e.g., a PCI function), andtherefore, the data structure is referred to as a function table entry(FTE). Although the examples herein refer to PCI functions, in otherembodiments, other adapter functions or adapters may be discovered, inaccordance with an aspect of the present invention.

As shown in FIG. 3A, in one example, a function table entry 300 is anentry in a function table 302 stored, for instance, in secure memory.Each function table entry 300 includes information to be used inprocessing associated with its adapter. In one example, function tableentry 300 includes one or more device table entry indices 310, each ofwhich is used as an index into the device table to locate itscorresponding device table entry (a PCI function may have a plurality ofaddress spaces assigned thereto, and therefore, a plurality of DTEs); abusy indicator 312 that indicates whether the PCI function is busy; apermanent error state indicator 314 that indicates whether the functionis in a permanent error state; a recovery initiator indicator 316 thatindicates whether recovery has been initiated for the function; apermission indicator 318 that indicates whether the operating systemtrying to enable the PCI function has authority to do so; an enableindicator 320 indicating whether the function is enabled (e.g.,1=enabled, 0=disabled); a group id 322 identifying a group to which theadapter belongs, if any; Base Address Registers (BARs) 1-N 324 used toindicate the base address of an I/O address space or memory space of theadapter (memory of an adapter may include one or more address spaces,including, for instance, a configuration space, an I/O space and/or oneor more memory spaces); sizes 1 . . . N 326 used in defining the size ofan adapter address space, as described below; start available DMA (SDMA)328 which indicates the beginning of an address space available for DMAoperations; and an end available DMA (EDMA) 330 which indicates the endof the address space.

In one example, the busy indicator, permanent error state indicator, andrecovery initiated indicator are set based on monitoring performed bythe firmware. Further, the permission indicator is set, for instance,based on policy. The BAR information and group id are based onconfiguration information discovered during the bus walk. The SDMA andEDMA are set by the firmware based on policy and details of theconfiguration. In other embodiments, the function table entry mayinclude more, less or different information, and the fields may be setby other mechanisms than described herein.

To locate a function table entry in a function table that includes oneor more entries, in one embodiment, a function handle is used. Forinstance, one or more bits of the function handle are used as an indexinto the function table to locate a particular function table entry.

Referring to FIG. 3B, additional details regarding a function handle aredescribed. In one example, a function handle 350 includes an enableindicator 352 that indicates whether the PCI function handle is enabled;a PCI function number 354 that identifies the function (this is a staticidentifier and may be used as an index into the function table); and aninstance number 356 which indicates the particular instance of thisfunction handle. For instance, each time the function is enabled, theinstance number is incremented to provide a new instance number.

In order for an operating system to use an adapter function, theoperating system performs discovery to obtain an indication of theadapter functions accessible to the operating system and to obtaininformation regarding those adapter functions. This processing isdescribed in further detail with reference to FIG. 4.

Referring to FIG. 4, one embodiment of a discover process is described.In one example, this logic is performed by a processor, responsive to arequest of an operating system that wishes to access an adapterfunction. Initially, responsive to executing the instruction, theoperating system obtains a list of adapter functions accessible to theoperating system, STEP 400. In one example, this list is obtained byissuing a Call Logical Processor instruction and specifying a listoperation, as described in further detail below. The list of adapterfunctions that are returned includes the function handles for thoseadapter functions.

Responsive to receiving the function handles, the operating systemselects an adapter function from the list, STEP 402, and obtainsattributes of that adapter function, STEP 404. In one example, thisinformation is obtained by issuing a Call Logical Processor instructionwith a query function operation, as described below. One of theattributes that may be returned is a group identifier. If a groupidentifier is returned, it identifies a group of one or more adapterfunctions for which this adapter function is included.

Assuming a group identifier is returned, the group identifier may beused to obtain common characteristics of the group, STEP 406. The groupcharacteristics may describe capabilities of the I/O infrastructureincluding, but not limited to, the I/O hub and the controlling firmware.In one example, this information is obtained by issuing a Call LogicalProcessor instruction with a query group operation, as described below.

Thereafter, a determination is made as to whether there are more adapterfunctions in the obtained list and whether the operating system wouldlike to find out additional information regarding another function,INQUIRY 408. If there is at least one additional adapter function forwhich the operating system would like to find out additionalinformation, then processing returns to STEP 402. Otherwise, thediscovery process is complete, STEP 410.

As described above, in one embodiment, to obtain the informationregarding an adapter function, a Call Logical Processor instruction isused. One embodiment of this instruction is depicted in FIG. 5A. Asshown, in one example, a Call Logical Processor (CLP) instruction 500includes an operation code 502 indicating that it is the Call LogicalProcessor instruction; and an indication for a command 504. In oneexample, this indication is an address of a request block that describesthe command to be performed, and the information in the request block isdependent on the command. Examples of requests blocks and correspondingresponse blocks for various commands are described with reference toFIGS. 5B-7B.

Referring initially to FIG. 5B, a request block for a list PCI functionscommand is provided. The list PCI functions command is used to obtain alist of PCI functions that are assigned to the requesting configuration(e.g., the requesting operating system). A request block 520 includes anumber of parameters, such as, for instance:

-   -   Length field 522: This field indicates the length of the request        block;    -   Command Code 524: This field indicates the list PCI functions        command; and    -   Resume Token 526: This field is an integer that is used to        either start a new list PCI functions command or resume a        previous list PCI functions command, as described in further        detail below.    -   When the resume token field in the command request block        includes, for instance, a value of zero, a new list of PCI        functions is requested. When the resume token field includes,        for instance, a non-zero value, which was returned from a        previous list PCI functions command, a continuation of a        previous list of PCI functions is requested.

Responsive to issuing and processing the Call Logical Processorinstruction for a list PCI functions command, a response block isreturned. One embodiment of the response block is depicted in FIG. 5C.In one example, a response block 550 for a list PCI functions commandincludes:

-   -   Length field 552: This field indicates the length of the        response block;    -   Response Code 554: This field indicates a status of the command;    -   PCI Function List 556: This field indicates a list of one or        more PCI functions available to the requesting operating system;    -   Resume Token 558: This field indicates whether a continuation of        a previous list of PCI functions is requested. In one example,        when the resume token in the request block and the resume token        in the response block are zero, all PCI functions assigned to        the requesting configuration are represented in the PCI function        list; if the resume token in the request block is zero and the        resume token in the response block is not zero, additional PCI        functions assigned to the request configuration may exist that        have not been represented in the list; if the resume token in        the request block is not zero and the resume token in the        response block is zero, from the resume point, remaining PCI        functions assigned to the requesting configuration are        represented in the list; when both the resume tokens in the        request and response block are not zero from the resume point,        additional PCI functions assigned to the requesting        configuration may exist that have not been represented in any        associated PCI function list. The resume token remains valid for        an indefinite period of time after being returned, but it may be        invalid due to a variety of model dependent reasons, including        system load elapse time;    -   Model Dependent Data 560: This field includes data that depends        on the system;    -   Number of PCI Functions 562: This field indicates the maximum        number of PCI functions supported by the facility; and    -   Entry Size 564: This field indicates the size of each entry in        the PCI function list.

Further details regarding the PCI function list are described withreference to FIG. 5D. In one example, the PCI function list includes aplurality of entries and each entry 556 includes the followinginformation, as an example:

-   -   Device ID 570: This field indicates the I/O adapter associated        with the corresponding PCI function;    -   Vendor ID 572: This field identifies the manufacturer of the I/O        adapter associated with the corresponding PCI function;    -   Function Identifier 574: This field includes a persistent        identifier of the PCI function;    -   Function Handle 576: This field identifies a PCI function. The        PCI function handle stored is a general handle when a specified        bit of the handle is zero, and it is an enabled handle when that        bit is one. If the PCI function is disabled, a general PCI        function handle is stored. If the PCI function is enabled, an        enabled PCI function handle is stored. A PCI function handle is        not, in one example, persistent beyond an IPL, which differs        from the PCI function ID, which is persistent and is set for the        life of the I/O configuration definition. Further details        regarding one embodiment of a function handle are described        above with reference to FIG. 3B; and    -   Configuration State 578: This field indicates the state of the        PCI function. When this indicator is, for instance, zero, the        state is standby, and when, for instance, one, the state is        configured. When in standby, the PCI function handle is the        general PCI function handle, and when configured, it is either        the general or enabled PCI function handle depending on whether        the PCI function is enabled.

Subsequent to obtaining the list of adapter functions, information maybe obtained regarding the attributes of a selected function asdesignated by a specified PCI function handle. This information may beobtained by issuing a CLP instruction with a query function command.

One embodiment of the request block for a query PCI function command isdescribed with reference to FIG. 6A. In one example, request block 600includes, for instance:

-   -   Length field 602: This field indicates the length of the request        block;    -   Command Code 604: This field indicates the query PCI function        command; and    -   Function Handle 606: This field includes the PCI function handle        (e.g., general or enabled) that designates the PCI function to        be queried.

Responsive to issuing the Call Logical Processor instruction for thequery PCI function command, a response block is returned. One embodimentof the response block is depicted in FIG. 6B. In one example, a responseblock 650 includes the following:

-   -   Length 652: This field indicates the length of the response        block;    -   Response Code 654: This field indicates a status of the command;    -   Function Group ID 656: This field indicates the PCI function        group identifier. A PCI function group identifier is used to        associate a group of PCI functions with a set of attributes        (also referred to herein as characteristics). Each PCI function        with the same PCI function group identifier has the same set of        attributes;    -   Function ID 658: The PCI function id is a persistent identifier        of the PCI function originally specified by the PCI function        handle and is set for the life of the I/O configuration        definition;    -   Physical Channel Adapter 660: This value represents a model        dependent identification of the location of the physical I/O        adapter which corresponds to the PCI function;    -   Base Address Registers (BARs) 1 . . . n 662: This field includes        a plurality of unsigned integers, designated as BAR_(o)-BAR_(n),        which are associated with the originally specified PCI function,        and whose values are also stored in the base address registers        associated with the PCI function. Each BAR specifies the        starting address of a memory space or I/O space within the        adapter, and also indicates the type of address space, that is        whether it is a 64 or 32 bit memory space, or a 32 bit I/O        space, as examples;    -   Size 1 . . . n 664: This field includes a plurality of unsigned        integers, designated as SIZE₀-SIZE_(n). The value of a Size        field, when non-zero, represents the size of each address space        with each entry corresponding to a previously described BAR.

Further details regarding BAR and Size are described below.

-   -   1. When a BAR is not implemented for a PCI function, the BAR        field and its corresponding size field are both stored as zeros.    -   2. When a BAR field represents either an I/O address space or a        32-bit memory-address space, the corresponding size field is        nonzero and represents the size of the address space.

3. When a BAR field represents a 64-bit memory address space,

-   -   -   a. The BAR_(n) field represents the least significant            address bits.        -   b. The next consecutive BAR_(n+1) field represents the most            significant address bits.        -   c. The corresponding SIZE_(n) field is nonzero and            represents the size of the address space.        -   d. The corresponding SIZE_(n+1) field is not meaningful and            is stored as zero.

    -   Start Available DMA 666: This field includes an address which        indicates the beginning of a range of PCI addresses that are        available for DMA operations;

    -   End Available DMA 668: This field includes a value which        indicates the end of a range of PCI addresses that are available        for DMA operations.

In addition to obtaining attributes regarding the specific adapterfunction, attributes may also be obtained regarding the group thatincludes this function. These common attributes may be obtained fromissuing a CLP instruction with a query PCI function group command. Thiscommand is used to obtain a set of characteristics that are supportedfor a group of one or more PCI functions designated by the specified PCIfunction group identifier. A PCI function group identifier is used toassociate a group of PCI functions with the same set of characteristics.One embodiment of request block for the query PCI function group commandis described with reference to FIG. 7A. In one example, request block700 includes the following:

-   -   Length field 702: This field indicates the length of the request        block;    -   Command Code 704: This field indicates the query PCI function        group command; and    -   Function Group ID 706: This field specifies the PCI function        group identifier for which attributes are to be obtained.

Responsive to issuing and processing the Call Logical Processorinstruction with a query PCI function group command, a response block isreturned. One embodiment of the response block is depicted in FIG. 7B.In one example, a response block 750 includes:

-   -   Length Field 752: This field indicates the length of the        response block;    -   Response Code 754: This field indicates a status of the command;    -   Number of Interruptions 756: This field indicates the maximum        number of consecutive MSI vector numbers (i.e., interruption        event indicators) that are supported by the PCI facility for        each PCI function in the specified PCI function group. The        possible valid values of the number of interruptions are in the        range of zero to 2,048, in one example;    -   Version 758: This field indicates the version of the PCI        specification that is supported by the PCI facility to which the        group of PCI functions designated by the specified PCI group        identifier are attached;    -   Frame 762: This field indicates the frame (or page) sizes        supported for I/O address translation;    -   Measurement Block Update Interval 764: This is a value        indicating the approximate time interval (e.g., in milliseconds)        at which the PCI function measurement block is updating;    -   DMA Address Space Mask 766: This is a value used to indicate        which bits in a PCI address are used to identify a DMA address        space; and    -   MSI Address 768: This is a value that is to be used for message        signal interruption requests.

The query list and function commands described above retrieveinformation from, for instance, the function table. At initializationtime, or after a hot plug of an adapter, firmware performs a bus walk todetermine the location of the adapter and determines its basiccharacteristics. This information is stored by the firmware into thefunction table entry (FTE) for each adapter. Accessibility to theadapter is determined based on policy set by a system administrator andis also set by firmware into the FTE. The query list and functioncommands can then retrieve this information and store it in theirrespective response blocks accessible to the operating system.

Further, the group information is based on a given system I/Oinfrastructure and the capabilities of the firmware and the I/O hub.This may be stored in the FTE or any other convenient location for laterretrieval during the query processing. In particular, the query groupcommand retrieves the information and stores it in its response blockaccessible to the operating system.

In one example, the group id is used to distinguish between levels of anI/O hub. For example, if a server is upgraded, any newer I/O hubs mayhave extended capabilities. Thus, PCI functions attached to an older I/Ohub might be in group 1, whereas PCI functions attached to the newer I/Ohub might be in group 2.

Described in detail herein, is a tiered query facility used to discoveran available I/O configuration to the operating system. It is used todiscover the adapter functions available to the operating system andinformation regarding adapter functions. In the first tier, the listcommand is used to provide a list of the PCI functions available to theoperating system. Each list entry represents a PCI function and isindicated by a PCI function handle. Using the handle of a selected PCIfunction, a second tier query function command is used that is directedto the specified PCI function having that handle. The informationreturned by the query function includes information that is or may beunique to the specified PCI function. It provides the functionalcharacteristics of the specified PCI function. Further, it may indicatethe group of one or more functions to which the specified PCI functionbelongs. The group ID value provided in this query can then be used inthe third tier, a query group command, to determine additionalcharacteristics that are common to any PCI function in the same group.The information obtained from the list and queries is obtained withoutany knowledge on the part of the operating system of the I/Oconfiguration including whether any adapter functions exist or areaccessible to the operating system, nor are any characteristics of theadapters known to the operating system.

In the embodiments described herein, the adapters are PCI adapters. PCI,as used herein, refers to any adapters implemented according to aPCI-based specification as defined by the Peripheral ComponentInterconnect Special Interest Group (PCI-SIG), including but not limitedto, PCI or PCIe. In one particular example, the Peripheral ComponentInterconnect Express (PCIe) is a component level interconnect standardthat defines a bi-directional communication protocol for transactionsbetween I/O adapters and host systems. PCIe communications areencapsulated in packets according to the PCIe standard for transmissionon a PCIe bus. Transactions originating at I/O adapters and ending athost systems are referred to as upbound transactions. Transactionsoriginating at host systems and terminating at I/O adapters are referredto as downbound transactions. The PCIe topology is based onpoint-to-point unidirectional links that are paired (e.g., one upboundlink, one downbound link) to form the PCIe bus. The PCIe standard ismaintained and published by the PCI-SIG.

Other applications filed on the same day include: U.S. Ser. No. ______,entitled “Translation Of Input/Output Addresses To Memory Addresses,”Craddock et al., (POU920090029US1); U.S. Ser. No. ______, entitled“Runtime Determination Of Translation Formats For Adapter Functions,”Craddock et al., (POU920100007US1); U.S. Ser. No. ______, entitled“Resizing Address Spaces Concurrent To Accessing The Address Spaces,”Craddock et al., (POU920100009US1); U.S. Ser. No. ______, entitled“Multiple Address Spaces Per Adapter,” Craddock et al.,(POU920100010US1); U.S. Ser. No. ______, entitled “Converting A MessageSignaled Interruption Into An I/O Adapter Event Notification,” Craddocket al., (POU920100014US1); U.S. Ser. No. ______, entitled “Converting AMessage Signaled Interruption Into An I/O Adapter Event Notification ToA Guest Operating System,” Brice et al., (POU920100015US1); U.S. Ser.No. ______, entitled “Identification Of Types Of Sources Of AdapterInterruptions,” Craddock et al., (POU920100016US1); U.S. Ser. No.______, entitled “Controlling A Rate At Which Adapter InterruptionRequests Are Processed,” Belmar et al., (POU920100017US1); U.S. Ser. No.______, entitled “Controlling The Selectively Setting Of OperationalParameters For An Adapter,” Craddock et al., (POU920100018US1); U.S.Ser. No. ______, entitled “Load Instruction for Communicating withAdapters,” Craddock et al., (POU920100019US1); U.S. Ser. No. ______,entitled “Controlling Access By A Configuration To An Adapter Function,”Craddock et al., (POU920100020US1); U.S. Ser. No. ______, entitled“Enable/Disable Adapters Of A Computing Environment,” Coneski et al.,(POU920100022US1); U.S. Ser. No. ______, entitled “Guest Access ToAddress Spaces Of Adapter,” Craddock et al., (POU920100023US1); U.S.Ser. No. ______, entitled “Managing Processing Associated With HardwareEvents,” Coneski et al., (POU920100025US1); U.S. Ser. No. ______,entitled “Operating System Notification Of Actions To Be TakenResponsive To Adapter Events,” Craddock et al., (POU920100026US1); U.S.Ser. No. ______, entitled “Measurement Facility For Adapter Functions,”Brice et al., (POU920100027US1); U.S. Ser. No. ______, entitled“Store/Store Block Instructions for Communicating with Adapters,”Craddock et al., (POU920100162US1); U.S. Ser. No. ______, entitled“Associating Input/Output Device Requests With Memory Associated With ALogical Partition,” Craddock et al., (POU920100045US1); U.S. Ser. No.______, entitled “Scalable I/O Adapter Function Level Error Detection,Isolation, And Reporting,” Craddock et al., (POU920100044US1); U.S. Ser.No. ______, entitled “Switch Failover Control In A MultiprocessorComputer System,” Bayer et al., (POU920100042US1); U.S. Ser. No. ______,entitled “A System And Method For Downbound I/O Expansion Request AndResponse Processing In A PCIe Architecture,” Gregg et al.,(POU920100040US1); U.S. Ser. No. ______, entitled “Upbound Input/OutputExpansion Request And Response Processing In A PCIe Architecture,” Gregget al., (POU920100039US1); U.S. Ser. No. ______, entitled “A System AndMethod For Routing I/O Expansion Requests And Responses In A PCIeArchitecture,” Lais et al. (POU920100038US1); U.S. Ser. No. ______,entitled “Input/Output (I/O) Expansion Response Processing In APeripheral Component Interconnect Express (PCIe) Environment,” Gregg etal., (POU920100037US1); U.S. Ser. No. ______, entitled “Memory ErrorIsolation And Recovery In A Multiprocessor Computer System,” Check etal., (POU920100041US1); and U.S. Ser. No. ______, entitled “ConnectedInput/Output Hub Management,” Bayer et al., (POU920100036US1), each ofwhich is hereby incorporated herein by reference in its entirety.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system”.Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readablestorage medium. A computer readable storage medium may be, for example,but not limited to, an electronic, magnetic, optical, electromagnetic,infrared or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

Referring now to FIG. 8, in one example, a computer program product 800includes, for instance, one or more computer readable storage media 802to store computer readable program code means or logic 804 thereon toprovide and facilitate one or more aspects of the present invention.

Program code embodied on a computer readable medium may be transmittedusing an appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programminglanguage, such as Java, Smalltalk, C++ or the like, and conventionalprocedural programming languages, such as the “C” programming language,assembler or similar programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

In addition to the above, one or more aspects of the present inventionmay be provided, offered, deployed, managed, serviced, etc. by a serviceprovider who offers management of customer environments. For instance,the service provider can create, maintain, support, etc. computer codeand/or a computer infrastructure that performs one or more aspects ofthe present invention for one or more customers. In return, the serviceprovider may receive payment from the customer under a subscriptionand/or fee agreement, as examples. Additionally or alternatively, theservice provider may receive payment from the sale of advertisingcontent to one or more third parties.

In one aspect of the present invention, an application may be deployedfor performing one or more aspects of the present invention. As oneexample, the deploying of an application comprises providing computerinfrastructure operable to perform one or more aspects of the presentinvention.

As a further aspect of the present invention, a computing infrastructuremay be deployed comprising integrating computer readable code into acomputing system, in which the code in combination with the computingsystem is capable of performing one or more aspects of the presentinvention.

As yet a further aspect of the present invention, a process forintegrating computing infrastructure comprising integrating computerreadable code into a computer system may be provided. The computersystem comprises a computer readable medium, in which the computermedium comprises one or more aspects of the present invention. The codein combination with the computer system is capable of performing one ormore aspects of the present invention.

Although various embodiments are described above, these are onlyexamples. For example, computing environments of other architectures canincorporate and use one or more aspects of the present invention. Asexamples, servers other than System z® servers, such as Power Systemsservers or other servers offered by International Business MachinesCorporation, or servers of other companies can include, use and/orbenefit from one or more aspects of the present invention. Further,although in the examples herein, the adapters and PCI hub are considereda part of the server, in other embodiments, they do not have tonecessarily be considered a part of the server, but can simply beconsidered as being coupled to system memory and/or other components ofa computing environment. The computing environment need not be a server.Further, the operating system may be an operating system of a specificpartition or zone, and thus, the information is obtained for thatpartition or zone. Further, other software (e.g., other privilegedsoftware) may be using one or more aspects of the present invention toobtain the information. Additionally, each request and response blockmay include more, less or different information, and other types ofinstructions may be used. Further, in other embodiments, the informationis obtained without use of an instruction. Many other variations arepossible.

Further, other types of computing environments can benefit from one ormore aspects of the present invention. As an example, a data processingsystem suitable for storing and/or executing program code is usable thatincludes at least two processors coupled directly or indirectly tomemory elements through a system bus. The memory elements include, forinstance, local memory employed during actual execution of the programcode, bulk storage, and cache memory which provide temporary storage ofat least some program code in order to reduce the number of times codemust be retrieved from bulk storage during execution.

Input/Output or I/O devices (including, but not limited to, keyboards,displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives andother memory media, etc.) can be coupled to the system either directlyor through intervening I/O controllers. Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodems, and Ethernet cards are just a few of the available types ofnetwork adapters.

Referring to FIG. 9, representative components of a Host Computer system5000 to implement one or more aspects of the present invention areportrayed. The representative host computer 5000 comprises one or moreCPUs 5001 in communication with computer memory (i.e., central storage)5002, as well as I/O interfaces to storage media devices 5011 andnetworks 5010 for communicating with other computers or SANs and thelike. The CPU 5001 is compliant with an architecture having anarchitected instruction set and architected functionality. The CPU 5001may have dynamic address translation (DAT) 5003 for transforming programaddresses (virtual addresses) into real addresses of memory. A DATtypically includes a translation lookaside buffer (TLB) 5007 for cachingtranslations so that later accesses to the block of computer memory 5002do not require the delay of address translation. Typically, a cache 5009is employed between computer memory 5002 and the processor 5001. Thecache 5009 may be hierarchical having a large cache available to morethan one CPU and smaller, faster (lower level) caches between the largecache and each CPU. In some implementations, the lower level caches aresplit to provide separate low level caches for instruction fetching anddata accesses. In one embodiment, an instruction is fetched from memory5002 by an instruction fetch unit 5004 via a cache 5009. The instructionis decoded in an instruction decode unit 5006 and dispatched (with otherinstructions in some embodiments) to instruction execution unit or units5008. Typically several execution units 5008 are employed, for examplean arithmetic execution unit, a floating point execution unit and abranch instruction execution unit. The instruction is executed by theexecution unit, accessing operands from instruction specified registersor memory as needed. If an operand is to be accessed (loaded or stored)from memory 5002, a load/store unit 5005 typically handles the accessunder control of the instruction being executed. Instructions may beexecuted in hardware circuits or in internal microcode (firmware) or bya combination of both.

As noted, a computer system includes information in local (or main)storage, as well as addressing, protection, and reference and changerecording. Some aspects of addressing include the format of addresses,the concept of address spaces, the various types of addresses, and themanner in which one type of address is translated to another type ofaddress. Some of main storage includes permanently assigned storagelocations. Main storage provides the system with directly addressablefast-access storage of data. Both data and programs are to be loadedinto main storage (from input devices) before they can be processed.

Main storage may include one or more smaller, faster-access bufferstorages, sometimes called caches. A cache is typically physicallyassociated with a CPU or an I/O processor. The effects, except onperformance, of the physical construction and use of distinct storagemedia are generally not observable by the program.

Separate caches may be maintained for instructions and for dataoperands. Information within a cache is maintained in contiguous byteson an integral boundary called a cache block or cache line (or line, forshort). A model may provide an EXTRACT CACHE ATTRIBUTE instruction whichreturns the size of a cache line in bytes. A model may also providePREFETCH DATA and PREFETCH DATA RELATIVE LONG instructions which effectsthe prefetching of storage into the data or instruction cache or thereleasing of data from the cache.

Storage is viewed as a long horizontal string of bits. For mostoperations, accesses to storage proceed in a left-to-right sequence. Thestring of bits is subdivided into units of eight bits. An eight-bit unitis called a byte, which is the basic building block of all informationformats. Each byte location in storage is identified by a uniquenonnegative integer, which is the address of that byte location or,simply, the byte address. Adjacent byte locations have consecutiveaddresses, starting with 0 on the left and proceeding in a left-to-rightsequence. Addresses are unsigned binary integers and are 24, 31, or 64bits.

Information is transmitted between storage and a CPU or a channelsubsystem one byte, or a group of bytes, at a time. Unless otherwisespecified, in, for instance, the z/Architecture®, a group of bytes instorage is addressed by the leftmost byte of the group. The number ofbytes in the group is either implied or explicitly specified by theoperation to be performed. When used in a CPU operation, a group ofbytes is called a field. Within each group of bytes, in, for instance,the z/Architecture®, bits are numbered in a left-to-right sequence. Inthe z/Architecture®, the leftmost bits are sometimes referred to as the“high-order” bits and the rightmost bits as the “low-order” bits. Bitnumbers are not storage addresses, however. Only bytes can be addressed.To operate on individual bits of a byte in storage, the entire byte isaccessed. The bits in a byte are numbered 0 through 7, from left toright (in, e.g., the z/Architecture). The bits in an address may benumbered 8-31 or 40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bitaddresses; they are numbered 0-63 for 64-bit addresses. Within any otherfixed-length format of multiple bytes, the bits making up the format areconsecutively numbered starting from 0. For purposes of error detection,and in preferably for correction, one or more check bits may betransmitted with each byte or with a group of bytes. Such check bits aregenerated automatically by the machine and cannot be directly controlledby the program. Storage capacities are expressed in number of bytes.When the length of a storage-operand field is implied by the operationcode of an instruction, the field is said to have a fixed length, whichcan be one, two, four, eight, or sixteen bytes. Larger fields may beimplied for some instructions. When the length of a storage-operandfield is not implied but is stated explicitly, the field is said to havea variable length. Variable-length operands can vary in length byincrements of one byte (or with some instructions, in multiples of twobytes or other multiples). When information is placed in storage, thecontents of only those byte locations are replaced that are included inthe designated field, even though the width of the physical path tostorage may be greater than the length of the field being stored.

Certain units of information are to be on an integral boundary instorage. A boundary is called integral for a unit of information whenits storage address is a multiple of the length of the unit in bytes.Special names are given to fields of 2, 4, 8, and 16 bytes on anintegral boundary. A halfword is a group of two consecutive bytes on atwo-byte boundary and is the basic building block of instructions. Aword is a group of four consecutive bytes on a four-byte boundary. Adoubleword is a group of eight consecutive bytes on an eight-byteboundary. A quadword is a group of 16 consecutive bytes on a 16-byteboundary. When storage addresses designate halfwords, words,doublewords, and quadwords, the binary representation of the addresscontains one, two, three, or four rightmost zero bits, respectively.Instructions are to be on two-byte integral boundaries. The storageoperands of most instructions do not have boundary-alignmentrequirements.

On devices that implement separate caches for instructions and dataoperands, a significant delay may be experienced if the program storesinto a cache line from which instructions are subsequently fetched,regardless of whether the store alters the instructions that aresubsequently fetched.

In one embodiment, the invention may be practiced by software (sometimesreferred to licensed internal code, firmware, micro-code, milli-code,pico-code and the like, any of which would be consistent with thepresent invention). Referring to FIG. 9, software program code whichembodies the present invention is typically accessed by processor 5001of the host system 5000 from long-term storage media devices 5011, suchas a CD-ROM drive, tape drive or hard drive. The software program codemay be embodied on any of a variety of known media for use with a dataprocessing system, such as a diskette, hard drive, or CD-ROM. The codemay be distributed on such media, or may be distributed to users fromcomputer memory 5002 or storage of one computer system over a network5010 to other computer systems for use by users of such other systems.

The software program code includes an operating system which controlsthe function and interaction of the various computer components and oneor more application programs. Program code is normally paged fromstorage media device 5011 to the relatively higher-speed computerstorage 5002 where it is available for processing by processor 5001. Thetechniques and methods for embodying software program code in memory, onphysical media, and/or distributing software code via networks are wellknown and will not be further discussed herein. Program code, whencreated and stored on a tangible medium (including but not limited toelectronic memory modules (RAM), flash memory, Compact Discs (CDs),DVDs, Magnetic Tape and the like is often referred to as a “computerprogram product”. The computer program product medium is typicallyreadable by a processing circuit preferably in a computer system forexecution by the processing circuit.

FIG. 10 illustrates a representative workstation or server hardwaresystem in which the present invention may be practiced. The system 5020of FIG. 10 comprises a representative base computer system 5021, such asa personal computer, a workstation or a server, including optionalperipheral devices. The base computer system 5021 includes one or moreprocessors 5026 and a bus employed to connect and enable communicationbetween the processor(s) 5026 and the other components of the system5021 in accordance with known techniques. The bus connects the processor5026 to memory 5025 and long-term storage 5027 which can include a harddrive (including any of magnetic media, CD, DVD and Flash Memory forexample) or a tape drive for example. The system 5021 might also includea user interface adapter, which connects the microprocessor 5026 via thebus to one or more interface devices, such as a keyboard 5024, a mouse5023, a printer/scanner 5030 and/or other interface devices, which canbe any user interface device, such as a touch sensitive screen,digitized entry pad, etc. The bus also connects a display device 5022,such as an LCD screen or monitor, to the microprocessor 5026 via adisplay adapter.

The system 5021 may communicate with other computers or networks ofcomputers by way of a network adapter capable of communicating 5028 witha network 5029. Example network adapters are communications channels,token ring, Ethernet or modems. Alternatively, the system 5021 maycommunicate using a wireless interface, such as a CDPD (cellular digitalpacket data) card. The system 5021 may be associated with such othercomputers in a Local Area Network (LAN) or a Wide Area Network (WAN), orthe system 5021 can be a client in a client/server arrangement withanother computer, etc. All of these configurations, as well as theappropriate communications hardware and software, are known in the art.

FIG. 11 illustrates a data processing network 5040 in which the presentinvention may be practiced. The data processing network 5040 may includea plurality of individual networks, such as a wireless network and awired network, each of which may include a plurality of individualworkstations 5041, 5042, 5043, 5044. Additionally, as those skilled inthe art will appreciate, one or more LANs may be included, where a LANmay comprise a plurality of intelligent workstations coupled to a hostprocessor.

Still referring to FIG. 11, the networks may also include mainframecomputers or servers, such as a gateway computer (client server 5046) orapplication server (remote server 5048 which may access a datarepository and may also be accessed directly from a workstation 5045). Agateway computer 5046 serves as a point of entry into each individualnetwork. A gateway is needed when connecting one networking protocol toanother. The gateway 5046 may be preferably coupled to another network(the Internet 5047 for example) by means of a communications link. Thegateway 5046 may also be directly coupled to one or more workstations5041, 5042, 5043, 5044 using a communications link. The gateway computermay be implemented utilizing an IBM eServer™ System z® server availablefrom International Business Machines Corporation.

Referring concurrently to FIG. 10 and FIG. 11, software programming codewhich may embody the present invention may be accessed by the processor5026 of the system 5020 from long-term storage media 5027, such as aCD-ROM drive or hard drive. The software programming code may beembodied on any of a variety of known media for use with a dataprocessing system, such as a diskette, hard drive, or CD-ROM. The codemay be distributed on such media, or may be distributed to users 5050,5051 from the memory or storage of one computer system over a network toother computer systems for use by users of such other systems.

Alternatively, the programming code may be embodied in the memory 5025,and accessed by the processor 5026 using the processor bus. Suchprogramming code includes an operating system which controls thefunction and interaction of the various computer components and one ormore application programs 5032. Program code is normally paged fromstorage media 5027 to high-speed memory 5025 where it is available forprocessing by the processor 5026. The techniques and methods forembodying software programming code in memory, on physical media, and/ordistributing software code via networks are well known and will not befurther discussed herein. Program code, when created and stored on atangible medium (including but not limited to electronic memory modules(RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and thelike is often referred to as a “computer program product”. The computerprogram product medium is typically readable by a processing circuitpreferably in a computer system for execution by the processing circuit.

The cache that is most readily available to the processor (normallyfaster and smaller than other caches of the processor) is the lowest (L1or level one) cache and main store (main memory) is the highest levelcache (L3 if there are 3 levels). The lowest level cache is oftendivided into an instruction cache (I-Cache) holding machine instructionsto be executed and a data cache (D-Cache) holding data operands.

Referring to FIG. 12, an exemplary processor embodiment is depicted forprocessor 5026. Typically one or more levels of cache 5053 are employedto buffer memory blocks in order to improve processor performance. Thecache 5053 is a high speed buffer holding cache lines of memory datathat are likely to be used. Typical cache lines are 64, 128 or 256 bytesof memory data. Separate caches are often employed for cachinginstructions than for caching data. Cache coherence (synchronization ofcopies of lines in memory and the caches) is often provided by various“snoop” algorithms well known in the art. Main memory storage 5025 of aprocessor system is often referred to as a cache. In a processor systemhaving 4 levels of cache 5053, main storage 5025 is sometimes referredto as the level 5 (L5) cache since it is typically faster and only holdsa portion of the non-volatile storage (DASD, tape etc) that is availableto a computer system. Main storage 5025 “caches” pages of data paged inand out of the main storage 5025 by the operating system.

A program counter (instruction counter) 5061 keeps track of the addressof the current instruction to be executed. A program counter in az/Architecture® processor is 64 bits and can be truncated to 31 or 24bits to support prior addressing limits. A program counter is typicallyembodied in a PSW (program status word) of a computer such that itpersists during context switching. Thus, a program in progress, having aprogram counter value, may be interrupted by, for example, the operatingsystem (context switch from the program environment to the operatingsystem environment). The PSW of the program maintains the programcounter value while the program is not active, and the program counter(in the PSW) of the operating system is used while the operating systemis executing. Typically, the program counter is incremented by an amountequal to the number of bytes of the current instruction. RISC (ReducedInstruction Set Computing) instructions are typically fixed length whileCISC (Complex Instruction Set Computing) instructions are typicallyvariable length. Instructions of the IBM z/Architecture® are CISCinstructions having a length of 2, 4 or 6 bytes. The Program counter5061 is modified by either a context switch operation or a branch takenoperation of a branch instruction for example. In a context switchoperation, the current program counter value is saved in the programstatus word along with other state information about the program beingexecuted (such as condition codes), and a new program counter value isloaded pointing to an instruction of a new program module to beexecuted. A branch taken operation is performed in order to permit theprogram to make decisions or loop within the program by loading theresult of the branch instruction into the program counter 5061.

Typically an instruction fetch unit 5055 is employed to fetchinstructions on behalf of the processor 5026. The fetch unit eitherfetches “next sequential instructions”, target instructions of branchtaken instructions, or first instructions of a program following acontext switch. Modern Instruction fetch units often employ prefetchtechniques to speculatively prefetch instructions based on thelikelihood that the prefetched instructions might be used. For example,a fetch unit may fetch 16 bytes of instruction that includes the nextsequential instruction and additional bytes of further sequentialinstructions.

The fetched instructions are then executed by the processor 5026. In anembodiment, the fetched instruction(s) are passed to a dispatch unit5056 of the fetch unit. The dispatch unit decodes the instruction(s) andforwards information about the decoded instruction(s) to appropriateunits 5057, 5058, 5060. An execution unit 5057 will typically receiveinformation about decoded arithmetic instructions from the instructionfetch unit 5055 and will perform arithmetic operations on operandsaccording to the opcode of the instruction. Operands are provided to theexecution unit 5057 preferably either from memory 5025, architectedregisters 5059 or from an immediate field of the instruction beingexecuted. Results of the execution, when stored, are stored either inmemory 5025, registers 5059 or in other machine hardware (such ascontrol registers, PSW registers and the like).

A processor 5026 typically has one or more units 5057, 5058, 5060 forexecuting the function of the instruction. Referring to FIG. 13A, anexecution unit 5057 may communicate with architected general registers5059, a decode/dispatch unit 5056, a load store unit 5060, and other5065 processor units by way of interfacing logic 5071. An execution unit5057 may employ several register circuits 5067, 5068, 5069 to holdinformation that the arithmetic logic unit (ALU) 5066 will operate on.The ALU performs arithmetic operations such as add, subtract, multiplyand divide as well as logical function such as and, or and exclusive-or(XOR), rotate and shift. Preferably the ALU supports specializedoperations that are design dependent. Other circuits may provide otherarchitected facilities 5072 including condition codes and recoverysupport logic for example. Typically the result of an ALU operation isheld in an output register circuit 5070 which can forward the result toa variety of other processing functions. There are many arrangements ofprocessor units, the present description is only intended to provide arepresentative understanding of one embodiment.

An ADD instruction for example would be executed in an execution unit5057 having arithmetic and logical functionality while a floating pointinstruction for example would be executed in a floating point executionhaving specialized floating point capability. Preferably, an executionunit operates on operands identified by an instruction by performing anopcode defined function on the operands. For example, an ADD instructionmay be executed by an execution unit 5057 on operands found in tworegisters 5059 identified by register fields of the instruction.

The execution unit 5057 performs the arithmetic addition on two operandsand stores the result in a third operand where the third operand may bea third register or one of the two source registers. The execution unitpreferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capableof performing a variety of logical functions such as Shift, Rotate, And,Or and XOR as well as a variety of algebraic functions including any ofadd, subtract, multiply, divide. Some ALUs 5066 are designed for scalaroperations and some for floating point. Data may be Big Endian (wherethe least significant byte is at the highest byte address) or LittleEndian (where the least significant byte is at the lowest byte address)depending on architecture. The IBM z/Architecture® is Big Endian. Signedfields may be sign and magnitude, 1's complement or 2's complementdepending on architecture. A 2's complement number is advantageous inthat the ALU does not need to design a subtract capability since eithera negative value or a positive value in 2's complement requires only anaddition within the ALU. Numbers are commonly described in shorthand,where a 12 bit field defines an address of a 4,096 byte block and iscommonly described as a 4 Kbyte (Kilo-byte) block, for example.

Referring to FIG. 13B, branch instruction information for executing abranch instruction is typically sent to a branch unit 5058 which oftenemploys a branch prediction algorithm such as a branch history table5082 to predict the outcome of the branch before other conditionaloperations are complete. The target of the current branch instructionwill be fetched and speculatively executed before the conditionaloperations are complete. When the conditional operations are completedthe speculatively executed branch instructions are either completed ordiscarded based on the conditions of the conditional operation and thespeculated outcome. A typical branch instruction may test conditioncodes and branch to a target address if the condition codes meet thebranch requirement of the branch instruction, a target address may becalculated based on several numbers including ones found in registerfields or an immediate field of the instruction for example. The branchunit 5058 may employ an ALU 5074 having a plurality of input registercircuits 5075, 5076, 5077 and an output register circuit 5080. Thebranch unit 5058 may communicate with general registers 5059, decodedispatch unit 5056 or other circuits 5073, for example.

The execution of a group of instructions can be interrupted for avariety of reasons including a context switch initiated by an operatingsystem, a program exception or error causing a context switch, an I/Ointerruption signal causing a context switch or multi-threading activityof a plurality of programs (in a multi-threaded environment), forexample. Preferably a context switch action saves state informationabout a currently executing program and then loads state informationabout another program being invoked. State information may be saved inhardware registers or in memory for example. State informationpreferably comprises a program counter value pointing to a nextinstruction to be executed, condition codes, memory translationinformation and architected register content. A context switch activitycan be exercised by hardware circuits, application programs, operatingsystem programs or firmware code (microcode, pico-code or licensedinternal code (LIC)) alone or in combination.

A processor accesses operands according to instruction defined methods.The instruction may provide an immediate operand using the value of aportion of the instruction, may provide one or more register fieldsexplicitly pointing to either general purpose registers or specialpurpose registers (floating point registers for example). Theinstruction may utilize implied registers identified by an opcode fieldas operands. The instruction may utilize memory locations for operands.A memory location of an operand may be provided by a register, animmediate field, or a combination of registers and immediate field asexemplified by the z/Architecture® long displacement facility whereinthe instruction defines a base register, an index register and animmediate field (displacement field) that are added together to providethe address of the operand in memory for example. Location hereintypically implies a location in main memory (main storage) unlessotherwise indicated.

Referring to FIG. 13C, a processor accesses storage using a load/storeunit 5060. The load/store unit 5060 may perform a load operation byobtaining the address of the target operand in memory 5053 and loadingthe operand in a register 5059 or another memory 5053 location, or mayperform a store operation by obtaining the address of the target operandin memory 5053 and storing data obtained from a register 5059 or anothermemory 5053 location in the target operand location in memory 5053. Theload/store unit 5060 may be speculative and may access memory in asequence that is out-of-order relative to instruction sequence, howeverthe load/store unit 5060 is to maintain the appearance to programs thatinstructions were executed in order. A load/store unit 5060 maycommunicate with general registers 5059, decode/dispatch unit 5056,cache/memory interface 5053 or other elements 5083 and comprises variousregister circuits, ALUs 5085 and control logic 5090 to calculate storageaddresses and to provide pipeline sequencing to keep operationsin-order. Some operations may be out of order but the load/store unitprovides functionality to make the out of order operations to appear tothe program as having been performed in order, as is well known in theart.

Preferably addresses that an application program “sees” are oftenreferred to as virtual addresses. Virtual addresses are sometimesreferred to as “logical addresses” and “effective addresses”. Thesevirtual addresses are virtual in that they are redirected to physicalmemory location by one of a variety of dynamic address translation (DAT)technologies including, but not limited to, simply prefixing a virtualaddress with an offset value, translating the virtual address via one ormore translation tables, the translation tables preferably comprising atleast a segment table and a page table alone or in combination,preferably, the segment table having an entry pointing to the pagetable. In the z/Architecture®, a hierarchy of translation is providedincluding a region first table, a region second table, a region thirdtable, a segment table and an optional page table. The performance ofthe address translation is often improved by utilizing a translationlookaside buffer (TLB) which comprises entries mapping a virtual addressto an associated physical memory location. The entries are created whenthe DAT translates a virtual address using the translation tables.Subsequent use of the virtual address can then utilize the entry of thefast TLB rather than the slow sequential translation table accesses. TLBcontent may be managed by a variety of replacement algorithms includingLRU (Least Recently used).

In the case where the processor is a processor of a multi-processorsystem, each processor has responsibility to keep shared resources, suchas I/O, caches, TLBs and memory, interlocked for coherency. Typically,“snoop” technologies will be utilized in maintaining cache coherency. Ina snoop environment, each cache line may be marked as being in any oneof a shared state, an exclusive state, a changed state, an invalid stateand the like in order to facilitate sharing.

I/O units 5054 (FIG. 12) provide the processor with means for attachingto peripheral devices including tape, disc, printers, displays, andnetworks for example. I/O units are often presented to the computerprogram by software drivers. In mainframes, such as the System z® fromIBM®, channel adapters and open system adapters are I/O units of themainframe that provide the communications between the operating systemand peripheral devices.

Further, other types of computing environments can benefit from one ormore aspects of the present invention. As an example, an environment mayinclude an emulator (e.g., software or other emulation mechanisms), inwhich a particular architecture (including, for instance, instructionexecution, architected functions, such as address translation, andarchitected registers) or a subset thereof is emulated (e.g., on anative computer system having a processor and memory). In such anenvironment, one or more emulation functions of the emulator canimplement one or more aspects of the present invention, even though acomputer executing the emulator may have a different architecture thanthe capabilities being emulated. As one example, in emulation mode, thespecific instruction or operation being emulated is decoded, and anappropriate emulation function is built to implement the individualinstruction or operation.

In an emulation environment, a host computer includes, for instance, amemory to store instructions and data; an instruction fetch unit tofetch instructions from memory and to optionally, provide localbuffering for the fetched instruction; an instruction decode unit toreceive the fetched instructions and to determine the type ofinstructions that have been fetched; and an instruction execution unitto execute the instructions. Execution may include loading data into aregister from memory; storing data back to memory from a register; orperforming some type of arithmetic or logical operation, as determinedby the decode unit. In one example, each unit is implemented insoftware. For instance, the operations being performed by the units areimplemented as one or more subroutines within emulator software.

More particularly, in a mainframe, architected machine instructions areused by programmers, usually today “C” programmers, often by way of acompiler application. These instructions stored in the storage mediummay be executed natively in a z/Architecture® IBM® Server, oralternatively in machines executing other architectures. They can beemulated in the existing and in future IBM® mainframe servers and onother machines of IBM® (e.g., Power Systems servers and System x®Servers). They can be executed in machines running Linux on a widevariety of machines using hardware manufactured by IBM®, Intel®, AMD™,and others. Besides execution on that hardware under a z/Architecture®,Linux can be used as well as machines which use emulation by Hercules,UMX, or FSI (Fundamental Software, Inc), where generally execution is inan emulation mode. In emulation mode, emulation software is executed bya native processor to emulate the architecture of an emulated processor.

The native processor typically executes emulation software comprisingeither firmware or a native operating system to perform emulation of theemulated processor. The emulation software is responsible for fetchingand executing instructions of the emulated processor architecture. Theemulation software maintains an emulated program counter to keep trackof instruction boundaries. The emulation software may fetch one or moreemulated machine instructions at a time and convert the one or moreemulated machine instructions to a corresponding group of native machineinstructions for execution by the native processor. These convertedinstructions may be cached such that a faster conversion can beaccomplished. Notwithstanding, the emulation software is to maintain thearchitecture rules of the emulated processor architecture so as toassure operating systems and applications written for the emulatedprocessor operate correctly. Furthermore, the emulation software is toprovide resources identified by the emulated processor architectureincluding, but not limited to, control registers, general purposeregisters, floating point registers, dynamic address translationfunction including segment tables and page tables for example, interruptmechanisms, context switch mechanisms, Time of Day (TOD) clocks andarchitected interfaces to I/O subsystems such that an operating systemor an application program designed to run on the emulated processor, canbe run on the native processor having the emulation software.

A specific instruction being emulated is decoded, and a subroutine iscalled to perform the function of the individual instruction. Anemulation software function emulating a function of an emulatedprocessor is implemented, for example, in a “C” subroutine or driver, orsome other method of providing a driver for the specific hardware aswill be within the skill of those in the art after understanding thedescription of the preferred embodiment. Various software and hardwareemulation patents including, but not limited to U.S. Pat. No. 5,551,013,entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.;and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored TargetRoutines for Emulating Incompatible Instructions on a Target Processor”,by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding GuestInstruction to Directly Access Emulation Routines that Emulate the GuestInstructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled“Symmetrical Multiprocessing Bus and Chipset Used for CoprocessorSupport Allowing Non-Native Code to Run in a System”, by Gorishek et al;and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object CodeTranslator for Architecture Emulation and Dynamic Optimizing Object CodeTranslation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825,entitled “Method for Emulating Guest Instructions on a Host ComputerThrough Dynamic Recompilation of Host Instructions”, by Eric Traut, eachof which is hereby incorporated herein by reference in its entirety; andmany others, illustrate a variety of known ways to achieve emulation ofan instruction format architected for a different machine for a targetmachine available to those skilled in the art.

In FIG. 14, an example of an emulated host computer system 5092 isprovided that emulates a host computer system 5000′ of a hostarchitecture. In the emulated host computer system 5092, the hostprocessor (CPU) 5091 is an emulated host processor (or virtual hostprocessor) and comprises an emulation processor 5093 having a differentnative instruction set architecture than that of the processor 5091 ofthe host computer 5000′. The emulated host computer system 5092 hasmemory 5094 accessible to the emulation processor 5093. In the exampleembodiment, the memory 5094 is partitioned into a host computer memory5096 portion and an emulation routines 5097 portion. The host computermemory 5096 is available to programs of the emulated host computer 5092according to host computer architecture. The emulation processor 5093executes native instructions of an architected instruction set of anarchitecture other than that of the emulated processor 5091, the nativeinstructions obtained from emulation routines memory 5097, and mayaccess a host instruction for execution from a program in host computermemory 5096 by employing one or more instruction(s) obtained in asequence & access/decode routine which may decode the hostinstruction(s) accessed to determine a native instruction executionroutine for emulating the function of the host instruction accessed.Other facilities that are defined for the host computer system 5000′architecture may be emulated by architected facilities routines,including such facilities as general purpose registers, controlregisters, dynamic address translation and I/O subsystem support andprocessor cache, for example. The emulation routines may also takeadvantage of functions available in the emulation processor 5093 (suchas general registers and dynamic translation of virtual addresses) toimprove performance of the emulation routines. Special hardware andoff-load engines may also be provided to assist the processor 5093 inemulating the function of the host computer 5000′.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiment with various modifications as are suited to theparticular use contemplated.

1. A computer program product for obtaining input/output (I/O) hardwareinformation, said computer program product comprising: a computerreadable storage medium readable by a processing circuit and storinginstructions for execution by the processing circuit for performing amethod comprising: responsive to execution of an instruction issued byan operating system, obtaining, by a processor of a computingenvironment, a list of one or more adapter functions of an I/Oconfiguration accessible by the processor, the operating system absentknowledge of an adapter configuration topology of adapter functions ofthe computing environment, and said list including one or more functionhandles corresponding to the one or more adapter functions; andresponsive to execution of an instruction issued by the operatingsystem, using a function handle of the one or more function handles toobtain one or more attributes regarding the adapter function identifiedby the function handle, the function handle usable by one or moreinstructions to access the adapter function corresponding to thefunction handle.
 2. The computer program product of claim 1, wherein theone or more attributes includes a group identifier identifying a groupof one or more adapter functions that includes the adapter function,wherein the one or more adapter functions of the group have one or morecommon characteristics.
 3. The computer program product of claim 2,wherein the one or more common characteristics comprise at least one ofa number of interruptions allowed for the one or more adapter functionsof the group, a measurement block update interval indicating how oftenmeasurement data is to be obtained for the one or more adapter functionsof the group, an indication of which portion of an address provided byan adapter function of the group is to identify an address spaceaccessible by the one or more adapter functions of the group, or aninterrupt address usable by the one or more adapter functions.
 4. Thecomputer program product of claim 1, wherein the one or more attributesinclude at least one of a function group identifier to identify a groupof one or more adapter functions to which this adapter function belongs,a function identifier of the adapter function, a physical indicatorindicating a physical location of the adapter function, one or more baseaddress registers for the adapter function, one or more size indicatorsspecifying one or more address space sizes for the adapter function, oran indication of the beginning and end of an address space available tothe adapter function.
 5. The computer program product of claim 1,wherein the function handle comprises an enable indicator, a functionnumber and an instance number, and is also used to locate a functiontable entry that provides one or more indicators for its associatedadapter function.
 6. The computer program product of claim 1, whereinthe obtaining comprises obtaining the list absent performing by anoperating system executing within the processor a bus walk of the I/Oconfiguration.
 7. The computer program product of claim 1, wherein theobtaining comprises obtaining a partial list of adapter functionsaccessible to the processor, and wherein the method further comprisesresuming the obtaining one or more times to obtain a complete list ofadapter functions accessible to the processor.
 8. The computer programproduct of claim 7, wherein the instruction employs a request controlblock, said request control block comprising a resume indicatorindicating whether the obtaining is a continuation of a previousobtaining of the list of adapter functions.
 9. The computer programproduct of claim 1, wherein at least an indication of the list isprovided in a response control block received by the processor, andwherein the response control block further includes at least one of aresume token indicating whether the obtaining of the list is to becontinued or whether a complete list has been obtained, an indication ofa number of adapter functions supported by the I/O configuration, or asize indicator specifying a size of each entry in the list.
 10. Thecomputer program product of claim 1, wherein the list of one or moreadapter functions comprises one or more entries, and each entry includesat least one of an identifier of an adapter associated with the adapterfunction corresponding to the entry, an identifier of a manufacturer ofthe adapter, an identifier of the adapter function, the function handle,or a configuration state indicator.
 11. A computer system for obtaininginput/output (I/O) hardware information, said computer systemcomprising: a memory; and a processor in communications with the memory,wherein the computer system is configured to perform a method, saidmethod comprising: responsive to execution of an instruction issued byan operating system, obtaining, by a processor of a computingenvironment, a list of one or more adapter functions of an I/Oconfiguration accessible by the processor, the operating system absentknowledge of an adapter configuration topology of adapter functions ofthe computing environment, and said list including one or more functionhandles corresponding to the one or more adapter functions; andresponsive to execution of an instruction issued by the operatingsystem, using a function handle of the one or more function handles toobtain one or more attributes regarding the adapter function identifiedby the function handle, the function handle usable by one or moreinstructions to access the adapter function corresponding to thefunction handle.
 12. The computer system of claim 11, wherein the one ormore attributes includes a group identifier identifying a group of oneor more adapter functions that includes the adapter function, whereinthe one or more adapter functions of the group have one or more commoncharacteristics.
 13. The computer system of claim 12, wherein the one ormore common characteristics comprise at least one of a number ofinterruptions allowed for the one or more adapter functions of thegroup, a measurement block update interval indicating how oftenmeasurement data is to be obtained for the one or more adapter functionsof the group, an indication of which portion of an address provided byan adapter function of the group is to identify an address spaceaccessible by the one or more adapter functions of the group, or aninterrupt address usable by the one or more adapter functions.
 14. Thecomputer system of claim 11, wherein the one or more attributes includeat least one of a function group identifier to identify a group of oneor more adapter functions to which this adapter function belongs, afunction identifier of the adapter function, a physical indicatorindicating a physical location of the adapter function, one or more baseaddress registers for the adapter function, one or more size indicatorsspecifying one or more address space sizes for the adapter function, oran indication of the beginning and end of an address space available tothe adapter function.
 15. The computer system of claim 11, wherein theobtaining comprises obtaining the list absent performing by an operatingsystem executing within the processor a bus walk of the I/Oconfiguration.
 16. The computer system of claim 11, wherein theobtaining comprises obtaining a partial list of adapter functionsaccessible to the processor, and wherein the method further comprisesresuming the obtaining one or more times to obtain a complete list ofadapter functions accessible to the processor.
 17. The computer systemof claim 11, wherein at least an indication of the list is provided in aresponse control block received by the processor, and wherein theresponse control block further includes at least one of a resume tokenindicating whether the obtaining of the list is to be continued orwhether a complete list has been obtained, an indication of a number ofadapter functions supported by the I/O configuration, or a sizeindicator specifying a size of each entry in the list.
 18. A method ofobtaining input/output (I/O) hardware information, said methodcomprising: responsive to execution of an instruction issued by anoperating system, obtaining, by a processor of a computing environment,a list of one or more adapter functions of an I/O configurationaccessible by the processor, the operating system absent knowledge of anadapter configuration topology of adapter functions of the computingenvironment, and said list including one or more function handlescorresponding to the one or more adapter functions; and responsive toexecution of an instruction issued by the operating system, using afunction handle of the one or more function handles to obtain one ormore attributes regarding the adapter function identified by thefunction handle, the function handle usable by one or more instructionsto access the adapter function corresponding to the function handle. 19.The method of claim 18, wherein the one or more attributes includes agroup identifier identifying a group of one or more adapter functionsthat includes the adapter function, wherein the one or more adapterfunctions of the group have one or more common characteristics.
 20. Themethod of claim 18, wherein the obtaining comprises obtaining a partiallist of adapter functions accessible to the processor, and wherein themethod further comprises resuming the obtaining one or more times toobtain a complete list of adapter functions accessible to the processor.